The invention is generally directed to a printer and in particular to a printer in which the print control functions and type fonts can be changed in accordance with the functioning of a computer or like apparatus (host machine).
The development of various types of computers has resulted in a variety of methods of controlling a printer by the host computer. The methods differ from one another in, for example, the style of characters, symbols or dot patterns and horizontal or vertical print position control. As a result, it is often necessary to change the printer control program in order to use the printer with a host computer designed to operate utilizing a different control method.
Conventional printers contain a print head driving circuit, a carriage (CR) motor driving circuit, a line feed (LF) motor driving circuit, a microprocessing unit (MPU) for controlling the overall operation of the printer, a random access memory (RAM), a control read-only memory (ROM) for storing instruction data for the MPU and controlling the printer, a character read-only memory (ROM) for storing the printing characters and an interface for connecting the printer to the host computer. All of these components are traditionally mounted on one or more fixed circuit boards. A change in any of these circuits requires a change in the board or boards. This is a major and expensive change. Because of the complexity of the circuits utilized in the printer, the development and implementation of a new program for a printer is often time consuming and expensive.
As a result of these problems, it has also been necessary to utilize several different production lines to produce printers with different specifications adapted to various types of printing control methods. Consequently, there are often production lines which are not being fully utilized. The difficulties raised by the changes in the specifications for the printers has also caused a problem in inventory control. In particular, some printers with certain specifications which are in demand tend to sell well and are in short supply while printers with other specifications which are not in the same demand are overstocked.
Accordingly, there is a need to provide a printer which can have its specifications easily changed, thereby both simplifying the production process and reducing inventory control problems.